Branched nanocrystals (NCs) enable high atomic surface exposure within a crystalline network that provides avenues for charge transport. This combination of properties makes branched NCs particularly suitable for a range of applications where both interaction with the media and charge transport are involved. Herein we report on the colloidal synthesis of branched ceria NCs by means of a ligand-mediated overgrowth mechanism. In particular, the differential coverage of oleic acid as an X-type ligand at ceria facets with different atomic density, atomic coordination deficiency, and oxygen vacancy density resulted in a preferential growth in the  direction and thus in the formation of ceria octapods. Alcohols, through an esterification alcoholysis reaction, promoted faster growth rates that translated into nanostructures with higher geometrical complexity, increasing the branch aspect ratio and triggering the formation of side branches. On the other hand, the presence of water resulted in a significant reduction of the growth rate, decreasing the reaction yield and eliminating side branching, which we associate to a blocking of the surface reaction sites or a displacement of the alcoholysis reaction. Overall, adjusting the amounts of each chemical, well-defined branched ceria NCs with tuned number, thickness, and length of branches and with overall size ranging from 5 to 45 nm could be produced. We further demonstrate that such branched ceria NCs are able to provide higher surface areas and related oxygen storage capacities (OSC) than quasi-spherical NCs.
Chemistry of Materials
This work was supported by the European Regional Development Funds and the Spanish MINECO project BOOSTER. T.B. is grateful for the FI-AGAUR Research Fellowship Program, Generalitat de Catalunya (2015 FI_B 00744). P.G. acknowledges the People Programme (Marie Curie Actions) of the FP7/2007-2013 European Union Program (TECNIOspring Grant Agreement No. 600388) and the Agency for Business Competitiveness of the Government of Catalonia, ACCIÓ. M.I. thanks AGAUR for Beatriu de Pinós postdoctoral grant (2013 BP-A00344). Z.L. thanks the China Scholarship Council for scholarship support.
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Berestok T, Guardia P, Blanco J, et al. Tuning branching in ceria nanocrystals. Chemistry of Materials. 2017;29(10):4418-4424. doi:10.1021/acs.chemmater.7b00896
Berestok, T., Guardia, P., Blanco, J., Nafria, R., Torruella, P., López Conesa, L., … Cabot, A. (2017). Tuning branching in ceria nanocrystals. Chemistry of Materials. American Chemical Society. https://doi.org/10.1021/acs.chemmater.7b00896
Berestok, Taisiia, Pablo Guardia, Javier Blanco, Raquel Nafria, Pau Torruella, Luis López Conesa, Sònia Estradé, et al. “Tuning Branching in Ceria Nanocrystals.” Chemistry of Materials. American Chemical Society, 2017. https://doi.org/10.1021/acs.chemmater.7b00896.
T. Berestok et al., “Tuning branching in ceria nanocrystals,” Chemistry of Materials, vol. 29, no. 10. American Chemical Society, pp. 4418–4424, 2017.
Berestok T, Guardia P, Blanco J, Nafria R, Torruella P, López Conesa L, Estradé S, Ibáñez M, De Roo J, Luo Z, Cadavid D, Martins J, Kovalenko M, Peiró F, Cabot A. 2017. Tuning branching in ceria nanocrystals. Chemistry of Materials. 29(10), 4418–4424.
Berestok, Taisiia, et al. “Tuning Branching in Ceria Nanocrystals.” Chemistry of Materials, vol. 29, no. 10, American Chemical Society, 2017, pp. 4418–24, doi:10.1021/acs.chemmater.7b00896.